German Patent No. 36 09 587 describes an apparatus for the recovery of solvent vapor from an air stream in a machine for treating fabric with an organic solvent in which a closed circulation loop runs from a processing container receiving the articles to be treated through an air cooler and an air heater back to the processing container.
A blower is provided to circulate the air stream and an adsorption unit is connectable by a plurality of pipes to the circulation loop to form a circulation branch substantially parallel to a portion of the circulation loop. The goods to be treated can be many different kinds, e.g. textiles in the case of dry cleaning, workpieces, electronic components and so forth in the case of degreasing, etc. As solvents fluorinated or chlorinated hydrocarbons, e.g. perchloroethylene, are common.
Upon drying of the goods in this apparatus the last residue of solvent gas is removed by adsorption from the air stream circulating over the goods in a closed circulation loop.
The regeneration of the adsorption unit required is effected with hot air in a closed circulation loop with the help of the air heater and air cooler present in the air shaft of the cleaning machine. The cost of the several space-consuming bypass pipes of this system is disadvantageous. Also the air shaft of the machine must be shut off from the container during each washing process with appropriately large shut off valves so that in washing solvent vapor welling up from the processing container is not forced into the desorption cycle occurring at this time.
In the known arrangement according to German Patent No. 214,153 and German Patent No. 34 12 007 it is disadvantageous that during the adsorption stage before admission to the adsorption unit the air must flow through an air heater so that the adsorber itself on shutting off the air heater as a result of thermal inertia is exposed to correspondingly heated air flowing through it and its adsorption capacity is reduced and/or it must be built correspondingly larger. The apparatus according to U.S. Pat. No. 4,251,923 has a gas recovery device comprising two adsorbers operating alternately.